Pump or motor with pressure loading



June 18, 1957 R. L. MILLER PUMP OR MOTOR WITH PRESSURE LOADING 2 Sheets-Sheet 1 Filed Oct. 13, 1953 .Inzen/ow W A? W J% W June 18, 1957 R. L. MILLER PUMP 0R MOTOR wrm PRESSURE LOADING 2 She ets-Sheet 2 Filed on. 13, 1953 United States Patent C) PUMP UR MUTOR WITH PRESSURE LOADING Robert L. Miller, Rockford, Ill., assignor to Geo. D. Roper Corporation, Rockford, Ill., a corporation of Illinois Application October 13, 1953, Serial No. 385,877

9 Claims. (Cl. 103-126) This invention relates to improvements in pressure loaded gear pumps or fluid motors.

Pressure loaded pumps, particularly those ofthe gear type, have come into extensive use because of their exceptionally high volumetric efliciencies, which render them capable of delivering high output pressures previously unattainable with rotary pumps. In conventional pressure loaded pumps there is provided a pair of axially movable pressure bushings or wear plates abutting against one end face of the gears and providing a pumping seal thereat. Fluid pressure, commonly a part of the pump output pressure, is applied against the back of these pressure bushings to urge their front faces against the adjacent end faces of the gears to maintain the fluid seal thereat'.

For various reasons of significant practical importance, in such conventional pressure loading arrangements the pressure loading force acting against the back of each pressure bushing and urging it toward the end face of the corresponding gear is distributed symmetrically across the pressure bushing. However, at the front face of the pressure bushings the opposing fluid pressure in the pumping chamber in which the gears operate is non-uniform across each pressure bushing. Here, there is an increasing pressure gradient extending. from the pump inlet passage to the pumping chamber, which is the minimum pressure, around to the discharge outlet of the pump, which is at the maximum pressure of the gradient. For this reason the net force on each pressure bushing at the pump inlet passage tending to move the pressure bushing toward the end face of the respective gear is substantially greater than the corresponding. net force on each pressure bushing at the discharge outlet. This force unbalance across the front face of each pressure bushing tends to cause it to tilt away from the endface of the corresponding gear at the discharge outlet, breaking the pumping seal thereat, which is precisely where the seal is needed most, and thereby nullifying to a large extent the benefits of pressure loading. In addition, since the pressure bushings are forced more tightly againstthe end faces of the gears at the inlet passage, the pressure bushings are subjected to excessive wear at these locations. The power required to operate the pump is increased because of this uneven wear across the front faces of the pressure bushings.

It is the purpose of the present invention to avoid these disadvantages formerly associated with pressure loaded pumps.

Accordingly, it is an object of the present invention to provide in a pressure loadedgear pump or fluid motor a novel and improved pressure loading arrangement for providing a pumping seal across end faces of the gears.

Also, it is an object of this invention to provide a novel pressure loaded gear pump or fluid motor having a single pressure loaded member arranged to provide an effective pumping seal across end faces of the gears.

Another object of this invention is to provide in a gear pump or fluid motor a novel pressure loading mecha- "ice nism for the purpose of providing a pumping seal across end faces of the gears which is not subject to tilting away from the gears at any portion of the pumping seal thereat.

Another object of this invention is to provide a novel pressure loaded gear pump or fluid motor in which frictional drag between the gears and the pressure loading arrangement is reduced to a minimum consistent with the maintenance of an effective pumping seal at the gears.

A further object of this invention is to provide in a gear pump or fluid motor a novel pressure loading arrangement which establishes a pumping seal across the peripheries of the gears, as well as across end faces of the gears.

A further object of this inventionis to provide in a gear pump or fluid motor anovel pressure loading ar-. rangement for establishing a pumping seal across the peripheries of the gears which automatically adjusts itself to maintain a close running. clearance for the gear peripheries throughout the operation of the pump or fluid motor.

Another object of this invention is to provide novel pressure loading mechanism for gear pumps or fluid motors which is readily adaptable to standard pumps or fluid motors with only a minimum of modification thereof and which does not add stringent dimensional tolerance requirements to such devices.

A more comprehensive understanding of the present invention, as well as additional objects and advantages thereof, will be apparent from the following description of a preferred embodiment illustrated in the accompanying drawings.

In the drawings:

Figure 1' is a longitudinal section through a gear pump or fluid motor according to the present invention;

Fig. 2 is an end view of the Fig. 1 device;

Fig. 3 is a section along the line 3-3 in Fig. 2, showing the novel pressure member of the present invention abutting against an end face of the gears at the low pressure side thereof;

Fig; 4 is an end view of this pressure member, viewedfrom the toothed peripheries of the gears in the Fig. 3 assembly;

Fig. 5 is a front view of this pressure member,- viewed from the opposite end of the gears;

Fig. 6 is a top view of the novel pressure member in the Fig; 3 assembly; and

Fig. 7 is a transverse section through the pump or fluid motor, taken along the line 7-7 in Fig. 1.

Referring to Fig. l, and assuming for purposes of description that the device is to be operated as a pump, the housing 10 is in the form of a casting defining a pair of intersecting cylindrical bores 11, 12 (Fig. 7) in which the rotary meshing gears 13, 14 are respectively located. Another casting 15 closes the opposite end of the housing bones and is bolted to casting 10 to form therewith a fluid tight casing. for the pump.

Gear 13 is formed with an integral journal 16 projecting from one end and supported for rotation by a journal bearing sleeve 17 located snugly within a cylindrical housing recess 18 extending from one end of housing bore 11. At the juncture of recess 18 and bore 11 the housing defines an end wall 19 spaced from the adjacent end face of gear 13 and defining a pressure chamber 19a to which that end face of gear 13 is exposed. Since bearing sleeve 17 is slightly longer than recess 18 it maintains gear 13 spaced from housing end wall 19.

From the opposite end face of gear 13 an integral journal 20 extends into a conventional bushing or wear plate 21 fastened securely in a cylindrical housing recess 22 :at the opposite end of bore 11. This bushing has an integral, transverse, annual flange 23 located in bore 11 between the adjacent end of gear Bend the housing end wall 24 formed at the juncture of the bore 11 and housing recess 22. The bushing flange 23 is cylindrical around substantially its entire periphery to fit snugly within housing bore 11 and is flattened at its lower end, at the intersection of the housing bores 11 and 12.

Gear 13 has an internal splined connection to a rotary drive shaft 26 which extendsthrough a suitable fluid seal, indicated generally at 27 and bearing 26a, to a connection to a suitable prime mover, such as an electric motor (not shown).

An integral trunnion 28 projects from one end of gear 14 and is supported for rotation by a sleeve 29 located snugly within a cylindrical housing recess 30 which extends from one end of housing bore 12, at the abovementioned bore end wall 19. Sleeve 29 is slightly longer than recess 30, so that it maintains the adjacent end face of gear 14 spaced from housing end Wall 19 and therefore exposed to the pressure in chamber 19a.

Another integral trunnion 31 extends from the opposite end of gear 14 into a bushing or Wear plate 32 fixedly located in a cylindrical housing recess 33 which extends from the opposite end of housing bore 12. This bushing has an integral transverse annular flange 34 located .in bore 12 between the end wall 24 and the adjacent end of gear 14. The bushing flange 34 is cylindrical around most of its periphery to fit snugly Within bore 12 and has a flattened upper end, at the intersection of the housing bores 11 and 12 where it :abuts against the flattened lower end of the flange 23 on bushing 22.

As best seen in Figs. 3 and 7, the pump housing casting 10 is formed with a low pressure suction inlet passage 36 and a high pressure discharge passage 37 located respectively on opposite sides of the meshing gears for passing fluid into and out of the housing bores 11 and 12.

Associated with the foregoing elements of the pressure loaded pump is the novel pressure member shown in Figs. 46 and positioned in the pump in the manner indicated in Figs. 3 and 7. This pressure member is in the form of a generally cylindrical plunger 40 cut away at its forward end to provide a flat face or shoulder 41 adapted to abut against the adjacent and faces of the gears 13, 14 at the low pressure side of the housing bores 11, 12. Face 41 extends at a degree angle to the longitudinal axis of plunger 40. Projecting forwardly beyond the shoulder 41 is a protruding nose 42 which defines intersecting arcuate faces 43, 44 shaped complementary to the respective toothed peripheries of the gears and adapted to extend contiguous thereto at the low pressure side of the gears. The arcuate faces 43, 44 intersect along a line extending perpendicular to face 41 and at an angle of 45 degrees to the longitudinal axis of pressure member 40. stricted flow passage 45 formed in nose 42 is adapted to pass fluid from the housing inlet passage 36 to the gears at their intersection. Bore 46 leads from passage 45 to a transverse shoulder 48 at the rear of plunger 40.

The pressure member 40 is located in a housing bore 49 which intersects the gear-containing housing bores 11, 12 at an angle of 45 degrees, as best seen in Fig. 3, at the low pressure side of these bores. An end cap 50 is threaded onto the housing casting 10 at the outer end of bore 49 and provides a recess 51 for locating the reduced stem 52 projecting integrally from the back end of plunger 40. A drilled passage 53 extends through end cap 50 and the housing casting 10 from recess 51 to the high pressure chamber 19a in the pump bores 11, 12 for supplying fluid under high pressure against the outer end of stem 52 to pressure load the pressure member 40 towards the gears. A compression coil spring 54 is located in recess 51 to bias the pressure member toward the gears. By virtue of the passage 46 in the pressure member which communicates with the suction inlet to the pump, low pressure is established at the back side of shoulder 48.

When properly pressure loaded, the pressure member 40 has its face 41 abutting against the end faces of gears 13 and 14 at the low pressure side of these gears and just across the mesh point of the gears to the high pressure side thereof. The pressure member face 41 termi- Arenates at the high pressure side of the gears just beyond the mesh point of the gears. Immediately above and below the fluid passage 45 (Fig. 7) the sealing face 41 on the pressure member 4% extends contiguous to the gear end faces at portions of the gears which at their peripheries are out of communication with passage 45, except by way of the inter-tooth spaces on the gears. These portions of the gears are under higher fluid pressure than passage 45 because the increasing pressure gradient around the pump begins immediately beyond the portions of the gears which communicate with passage 45. Thus, the face 41 on pressure member 40 maintains a pumping seal across the adjacent end faces of the gears between high fluid pressure areas around the gears and the low pressure passage 45. However, the area of face 41 is a minimum consistent with the maintenance of an effective pumping seal across the end faces of the gears, so that the frictional drag of the gears against this face of pressure member 40 is thereby also minimized.

In the operation of the pump, the chamber 19a communicates with the discharge side of the gears and receives fluid under high pressure which acts against the adjacent end faces of the gears to pressure load the gears against the bushing flanges 23 and 34, where the opposite end faces of the gears have a minimum running clearance. At the low pressure side of the gears the face 41 on pressure member 40 is pressure loaded against the portions of the end faces of gears 13 and 14 remote from bushing flanges 23 and 34 which are not in direct communication with chamber 19a. At face 41 the pressure member 40 extends contiguous to the end faces of the gears from the portions of the gears which at their peripheries communicate with the suction inlet passage 36, 45 to portions of the gears which at their peripheries are immediately above and below the inlet passage but out of communication therewith, as well as across the mesh point of the gears to high pressure side thereof. Thus, the pressure member maintains an effective pumping seal at these end faces of the gears which prevents substantial leakage across these end faces from any of the high pressure areas on the gears around to the low pressure inlet passage 36, 45.

Because of the 45 degree disposition of the recess 49 in which pressure member 40 is located, when the pressure member is pressureloaded toward the gears their arcuate faces 43 and 44 are moved into contiguous relation with the peripheries of the gears to provide a pumping seal thereat. These arcuate faces on the pressure member are worn by the gear teeth to conform exactly to the outer diameter of the gears. This relationship is maintained throughout the lifeof the pump.

In this assembly there is no tipping force on pressure member 40 tending to tilt it away from the adjacent end faces of the gears because the pressure gradient forces acting against its face 41 are symmetrical about the axis of the pressure member. In addition, the gear drag forces on face 41 cancel each other out because of the opposite rotation of the gears.

From the foregoing it will be apparent that the novel pressure loading arrangement disclosed herein requires very little modification of a conventional gear pump for incorporation therein. In addition, the assembly and operation of the pump is simplified because only a single movable pressure loaded member is required.

It is to be understood that the location of the pressure at the low inlet pressure. Without further explanation it should be readily apparent that the pressure member 40 in such a modified arrangement would as eflectively maintain a pumping seal between the high and low pressure areas of the gears as in the previously described arrangement.

Likewise, from the foregoing it should be clear that the device may be operated as a fluid motor, rather than as a .pump, if desired.

While in the foregoing description and the accompanying drawings there is disclosed a specific embodiment of the present invention, it is to be understood that the invention is susceptible of various modifications, omissions and refinements departing from the disclosed embodiment without departing from the spirit and scope of this invention.

I claim:

1. In a pump, the combination of a pair of meshing rotary gears, a housing enclosing said gears and having a low pressure passage and a high pressure passage at opposite sides of the meshing gears, a pressure member slidably and guidably mounted in said housing for movement in a path extending at an acute angle to a plane through the axes of said gears, said pressure member having a first flat face extending contiguous to a portion of one of the end faces of each of said gears and a second curved face extending contiguous to a portion of the peripheries of said gears, and means for applying pressure to said pressure member to move the latter in said path towards said gears and urge said first face into engagement with the end face of the gear and said second face into engagement with the gear peripheries to form a pumping seal thereat.

2. In a pump, the combination of a pair of meshing rotary gears, a housing enclosing said gears and having a low pressure passage and a high pressure passage at opposite sides of the meshing gears, a pressure member slidably and guidably mounted in said housing for movement in a path extending at an acute angle to a plane through the axes of said gears, said pressure member having a first flat face extending contiguous to a portion of one of the end faces of each of said gears and a second curved face extending contiguous to a portion of the peripheries of said gears, means in said housing defining an end wall adjacent the other end faces of said gears, and means for applying pressure to said pressure member to move the latter along said path towards said gears and urge said first face into engagement with the adjacent end faces of the gears and said second face into engage- I ment with the gear peripheries to form a pumping seal thereat, said pressure member also urging said gears towards said end wall to provide a pumping seal at said other end faces of the gears.

3. In a pump, the combination of a pair of meshing rotary gears, a housing including a perimetric wall surrounding the gear peripheries and spaced end walls on opposite sides of said gears, said housing having inlet and discharge passages formed therein at opposite sides of the mesh point of the gears and a recess formed in one of said end walls and in the adjacent portion of said perimetric Wall, a pressure member slidably mounted in said recess for movement therein in a path disposed at an acute angle to a plane through the axes of said gears and in a plane through the mesh point of the gears and transverse to said first mentioned plane, said pressure member having an outer end thereof formed with a flat end face extending contiguous to a portion of one end face of each of the gears and a curved face extending contiguous to a portion of the gear peripheries, and means for applying pressure to said pressure member to move the latter in said path towards said gears and thereby urge said flat face on the pressure member against the adjacent end faces of the gears and said curved face on the pressure member against the gear peripheries to form a pumping seal thereat, said gears being mounted for 6 limited axial movement in said housing whereby said pressure me'r'nber engages one end face of the gears and urgesthe' gears against the remote end wall of the housing to form a pumping seal at the other end face of the gears 4-. The combination of claim 3 wherein said pressure member engages the walls of said recess and forms a pressure chamber therewith, said means for applying pressure to said member including means for conveying fluid under pressure from the discharge passage to said recess to pressure load said member against said gears.

5. In a pump, the combination of a pair of meshing rotary gears, a housing including a perimetric wall surrounding the gear peripheries and spaced end walls on opposite sides of said gears, said housing having inlet and discharge passages formed therein at opposite sides of the mesh point of the gears and a recess formed in one of said end walls and in the adjacent portion of said perimetric wall, a pressure member slidably mounted in said recess for movement therein in a path disposed at an acute angle to a plane through the axes of said gears and in a plane through the mesh point of the gears and transverse to said first mentioned plane, said pressure member having an outer end thereof formed with a flat end face extending contiguous to a portion of one end face of each of the gears and a curved face extending contiguous to a portion of the gear peripheries, means for applying fluid under pressure from the inlet passage to a portion of the area at the inner end of said pressure member within said recess, and means for applying fluid under pressure from said discharge passage to a different portion of the area at the inner end of said pressure member within said recess to move said pressure member along said path towards said gears and urge said flat face on the pressure member against the adjacent end faces of the gears and said curved face on the pressure member against the gear peripheries to form a running seal thereat.

6. The combination of claim 5 including spring means engaging the inner end of said pressure member for urging the latter against said gears.

7. In a gear pump, the combination of a pair of meshing gears, a housing including a perimetric wall surrounding the gear peripheries and spaced end walls on opposite sides of said gears defining a pump chamber, said housing having inlet and discharge passages formed therein, said housing having a recess formed therein and intersecting the pump chamber at one side of the gear peripheries and at one end of the gears adjacent the mesh point of the gears, a pressure member slidably mounted in said recess for movement therein in a path disposed at an acute angle to a plane through the axes of the gears and in a plane through the mesh point of said gears transverse to said first mentioned plane, said pressure member having one end thereof formed with a flat face extending contiguous to said one end face of the gears from a point adjacent the mesh point of the gears to a point adjacent one pressure passage but out of communication therewith, said pressure member having a curved face extending contiguous to the portion of the gear peripheries adjacent said one pressure passage, said pressure member having a piston extending from the other end thereof, said pressure member and said piston engaging the walls of said housing to define therewith first and second pressure chambers adjacent different areas on said other end of the pressure member, means for applying fluid under pressure from one of said pressure passages to one of said chambers, and means for applying fluid under pressure from the other of the pressure passages to the other of said chambers.

8. In a gear pump, the combination of a pair of meshing gears, a housing including a perimetric wall surrounding the gear peripheries and spaced end walls on opposite sides of said gears defining a pump chamber, said housing having inlet and discharge passages formed therein,

said housing having a recess formed therein and intersecting the pump chamber at one side of the gear peripheries and at one end of the gears adjacent the mesh point of the gears, a pressure member slidably mounted in said recess for movement therein in a path disposed at an acute angle to a plane through the axes of the gears and in a plane through the mesh point of said gears transverse to said first mentioned plane, said pressure member having one end thereof formed with a fiat face extending contiguous to said one end face of the gears from a point adjacent the mesh point of the gears to a point adjacent one pressure passage but out of communication therewith, said pressure member having a curved face extending contiguous to the portion of the gear peripheries adjacent said one pressure passage, said pressure member having a piston extending from the other end thereof, said pressure member and said piston engaging the walls of said housing to define therewith first and second pressure chambers adjacent different areas on said other end of the pressure member, a passage extending through said pressure member for applying fluid under pressure from one of said pressure passages to one of said chambers, and means for applying fluid under pressure from the other of said pressure passages to the other of said chambers.

9. The combination of claim 7 wherein said pressure member is movable at a 45 angle to the plane through the axes of said gears.

References Cited in the file of this patent UNlTED STATES PATENTS 2,105,259 Oshei Jan. 11, 1938 2,146,395 Horton Feb. 7, 1939 2,147,777 Oshei Feb. 21, 1939 2,211,154 Oshei Aug. 13, 1940 2,252,661 Oishei Aug. 12, 1941 2,622,534 Johnson Dec. 23, 1952 2,639,672 Johnson May 26, 1953 

